The K7RA Solar Update
This is a follow-up to last Wednesday’s pre-Thanksgiving bulletin. It was a little too early to provide the complete Thursday through Wednesday sunspot, solar flux and A index that normally appears in Friday’s bulletin, so we are including it today.
Our exciting period of nearly daily sunspot activity ended with the first spotless day on November 23 and the Sun has been blank since then. A look at the STEREO image shows a bright active area, perhaps five days over the eastern horizon, but we don't know if that will give us sunspots or not. Sunspot numbers for November 19-25 were 30, 31, 14, 13, 0, 0 and 0 with a mean of 12.6. The 10.7 cm flux was 76.7, 76.2, 75.8, 76.3, 75.7, 74.7 and 74.2 with a mean of 75.7. The estimated planetary A indices were 2, 1, 8, 4, 0, 6 and 5 with a mean of 3.7. The estimated mid-latitude A indices were 0, 2, 6, 2, 0, 3 and 4 with a mean of 2.4.
As the two STEREO craft move further from Earth, the visual gap on the Sun's far side is gradually closing; we look forward to the time in 2011 when all of the Sun will be visible from STEREO and Earth; currently the gap is about 14.3 percent. You can calculate the approximate percentage of the Sun in that dark spot by using the "Where is STEREO?" link on the STEREO home page. Check the "Separation angle A with B" stat at the bottom, subtract that number from 180, divide the result by 360 then multiple that result by 100 to get a percentage figure. You can check future dates by clicking on the "STEREO Orbit Tool" link. When you check February 1, 2010 at 0000 UTC, it yields a separation angle of 135.197 degrees. Subtracted from 180 degrees, this yields 44.803. Divide that by 360, then multiply by 100 and you get approximately 12.45 percent remaining on the dark side. October 1, 2010 yields 5.58 percent and January 1, 2011 is just 1.26 percent in the dark. Check the arithmetic!
Kent Tobiska, president of Space Environment Technologies in Pacific Palisades, California, sent in a link with some interesting products and resources for those interested in HF radio propagation. And for iPhone users, they have a very inexpensive (under $2) iPhone app for viewing real-time space weather data. See it here or from a link on their home page. Kent is also associated with the Space Weather Center at Utah State University' their Web site is currently under construction.
WorldRadio Online posts a new issue on the 20th of each month, and each has a column on propagation by Carl Luetzelschwab, K9LA. You can download it here and read Carl's article on "The Impact of Deep Solar Minimum on 160m Propagation." Carl's column begins on page 28 of the current December issue. The January 2010 issue should appear online on December 20.
Past bulletins have mentioned the incredible WSPR mode for weak signal communication. Doug Hawkins, W3HH, of Ocala, Florida, was using WSPR mode on November 18 on 30 meters and copied AA1A in Marshfield, Massachusetts -- 1105 miles away. Not unusual, except that AA1A was running only 10 µW. Doug points out that this signal is 20 dB below 1 mW! Doug says that several other stations have copied AA1A, but so far this is the longest distance record. Doug thought the distance was about 900 miles, but I looked up the address for each station at the top of the ARRL Web page then plugged the addresses into a computer atlas to find the exact latitude and longitude coordinates. I then used W6ELprop to calculate the distance, which turned out to be more than 24 percent further than Doug's estimate.
Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears each Thursday in The ARRL Letter. Check here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail.